The present invention relates generally to a heat exchanger, and in particular to a rotary-type counter-current heat exchanger for exchanging the heat by flowing supply air stream on one side of a center of rotation of a revolving heat exchanging element and flowing an exhaust air stream on the other side in an opposing manner.
Generally, a conventional rotary-type counter-current heat exchanger consists of dividing a cylindrical heat exchanging element rotatably supported in a casing into semicircular portions by means of a center channel, feeding the supply air stream to one side of the thus separated portions and feeding the exhaust air stream to the other side in an opposing manner, and rotating said heat exchanging element so that the heat is continuously exchanged.
In recent years, the heat exchangers of this type have been drawing attention as energy-saving devices because of their installation cost per unit quantity of heat conduction and high heat-recovering efficiency as compared to the heat exchangers of other types.
The heat exchangers of this type have so far employed a heat exchanging element composed of knitting a metal wire in the form of a mesh, or creasing and folding an asbestos paper and laminating it in the form of a beehive. The rotary frame for accomodating the thus prepared heat exchanging elements was usually formed in a cylindrical form, whereby the former heat exchanging element was usually accomodated in a plurality of matrixes formed by dividing the cylindrical rotary frame in the radial direction, and the latter heat exchanging element was usually wound and laminated in said cylindrical rotary frame in concentric with the center of rotation of said frame.
In the heat exchanger of such matrix setup, the sealing between the supply air stream and the exhaust air stream is attained by studding rubber strips called radial seal on one end of each of the matrixes. In the heat exchanger of the laminated construction, on the other hand, the sealing between the supply air stream and the exhaust air stream is attained by providing a ring-like rubber seal on the inner side of the center channel, or by providing a ring-like rubber seal at a suitable place of the casing along the circumferential surface of the heat exchanging element.
Further, the conventional heat exchangers of this type are equipped with a purge sector which works to capture the exhaust air stream that tends to migrate toward the side of supplying the air and return it back to the exhaust air side, in order to prevent the contaminated exhaust air stream from being mixed into the fresh supply air stream beyond the center channel.
However, such a conventional rotary heat exchanger posseses the following fundamental defects. That is, although the heat exchanging element made up of the aforesaid metals exhibited excellent sensible heat efficiency, it was not capable of exchanging the latent heat, resulting in very poor heat-exchanging efficiency as a whole. The heat exchanging element using the asbestos paper, on the other hand, could not be said as a desirable heat exchanging element employing asbestos which is hazardous to the human body and presenting a probability of detonation. Furthermore, the heat exchanging element using the asbestos had to be coated with large amounts of deliquescent salt such as expensive lithium chloride (LiCl) for efficiently carrying out the exchange of latent heat.
Moreover, in the case of the heat exchanging element using the laminate of asbestos papers creased to a pleat in a manner of beehive structure, oil, mist, dirt and dust are gradually accumulated over the entire heat exchanging element as it is used for extended periods of time, causing the heat exchanging efficiency of the heat exchanging element to be inevitably decreased. If the heat exchanging element is washed with water in order to recover the heat exchanging efficiency, the aforesaid deliquescent salt such as lithium chloride which is a medium for exchanging the latent heat is dissolved. Therefore, the maintenance was virtually very difficult. In other words, there was no drastical measure for recovering the heat exchanging efficiency except to replace the heat exchanging element with a new one.
In the case of the heat exchanging element of a metallic member arrayed in a matrix configuration, on the other hand, it was not allowed to clean the element from the radial direction of the rotary frame accomodating the heat exchanging element due to its construction. That is, in order to clean the element, the duct connected to the casing of the heat exchanger had to be removed, requiring cumbersome operation. In any way, it was very difficult to maintain the heat exchanging efficiency of the heat exchanger always in an optimum condition.
Moreover, the heat exchanger using a heat exchanging element made up of metal wires arrayed in a matrix configuration as mentioned above, required the sealing of a very complicated construction between the supply air stream and the exhaust air stream to play an important role as a structure of the heat exchanger of this sort. Particularly, as is well known, the operation for installing the aforesaid radial sealing in the heat exchanger required the most troublesome operation, giving a major cause of interrupting the rationalization of the operation for assembling the rotary-type heat exchangers of this sort.
Furthermore, referring to the structure of a conventional purge sector installed for the heat exchangers of this sort, strict limitation was imposed on the arrangement of a blower for properly functioning the purge sector, presenting considerable inconvenience.